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This 17 year old female presented in a confused state. There is no history of the events that preceded her arrival.   Her vital signs are normal.  Describe the findings in her ECG (ECG_0004). 

The ventricular rate is about 94 beats per minute, and the rhythm is regular.  P waves are not clearly visible
The QRS complexes are widened (about 0.16 seconds in V2), so there is an intraventricular conduction delay.  
The QRS complexes in the frontal leads show:

  • R waves, s waves  and ST depression  in I-III and aVF
  • Small qs waves  in aVL
  • Prominent R waves in aVR, with an R wave amplitude of nearly 3 mm and a width at least 0.08 seconds. The ST segment is also elevated in aVR.

Magnified view of aVR from ECG_0004

The frontal plane axis is  about +90 degrees, which is within normal limits for the patient’s age.

The QRS complexes in the precordial  leads show:

  • Mono-phasic R waves and s waves  in all the V leads. The transition zone is in V2, which has a RS pattern.  
  • The ST segments show (an upward sloping) depression in all the V leads
  • The mono-phasic R in the precordial leads and the s waves in I and V6 are consistent with a RBBB type  of intraventricular conduction delay.

A magnified section of the rhythm strip is showed below.

Careful examination of the rhythm strip (II) shows:

  • Slight hump in the downstroke of each T wave (red arrow)  that is (very likely) a P wave.
  • Prolonged QT interval.

Two possible measurements of the QT interval  are shown:

  • B, extending from the start of the Rs complex to the start of the P wave
  • C,  extending from the start of the Rs complex to the end of the T wave

Comparison of the R-R interval (A) with either of the two methods of measuring the QT interval (B or C) shows that the QT interval is prolonged.  The calculated QTc interval (using the Bazett  formula) for B is 600 msecond and for C is 700 msecond.

Summary:
There is a RBBB type intraventricular conduction disorder (with a QRS duration of 0.16 seconds) and a  markedly prolonged QT interval.  The prominent and wide R wave in aVR is similar to the changes seen in tricyclic antidepressant overdose.
At the observed ventricular rate of 94 beats per minute we would expect to see P waves,  if they were present.  The rhythm strip in this case could thus be interpreted in two ways:  P waves are not clearly seen (the Bulldog Drummond approach - see below) or they are largely hidden in the T wave (the Scarlet Pimpernel view - see below).  If we decide that P waves are not present our final diagnosis is accelerated  idioventricular rhythm.  If we decide that P waves are present we conclude that sinus rhythm is present,  but we still are left with the issue of the heart rate.
What heart rate value should we use to define the presence of “tachycardia”?  For sinus rhythms  the upper value of the resting heart rate in a healthy adult is listed in textbooks as 100 beats per minute.  Some have proposed that this upper value should be 90 beats per minute, which I think has considerable merit (Reference). If we accept this lower value then we conclude that the ECG of this patient shows sinus tachycardia as well as  RBBB type intraventricular conduction disorder and a prolonged QT interval.

Final Diagnosis: Sinus tachycardia,  RBBB type intraventricular conduction disorder, prolonged QT interval. The changes in aVR are suggestive of tricyclic antidepressant toxicity.

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Tweety (Bird) - an  androgynous yellow canary with a speech impediment -  was one of the animated characters in the Looney Tunes and Merrie Melodies cartoon series.  He was the object of desire of Sylvester, a bumptious cat who had difficulty pronouncing “s” and “p”.  The name "tweety" is a play on words, as it originally meant "sweetie".

Common Sense and the Balls of Bulldog Drummond
Hugh “Bulldog” Drummond is a fictional  British gentleman adventurer created by H.C. McNeile, who used the pen name of “Sapper”.  Bulldog Drummond is a First World War veteran, brutalized first by his public school  education and then by trench warfare.  Drummond is the  literary archetype of a  certain type of hero in English fiction:  patriotic, loyal,  and "physically and morally intrepid”.  Bored with his post-war lifestyle  Drummond publishes an advertisement looking for adventure, and soon finds himself involved in a series of exploits.
Drummond is large, very strong and is a  "apparently brainless hunk of a man”.  However  he is blessed with common sense, which allows him to beat his opponents, even if they are more clever.
What is the link between Bulldog Drummond and the ECG?  The first Bulldog Drummond novel was published in 1920, the same year that Thomas Lewis published his classic textbook “The Mechanism and Graphic Registration of the Heart Beat”.  While Sapper would not have read Lewis’s book,  Lewis  may have read  (and enjoyed) the Bulldog Drummond novel.  
Now consider BD’s attributes: muscle bound, a personality disorder, a small brain, large testicles, and lots of common sense. Two of these characteristics are useful when you are looking for evidence of P wave activity in a  ECG with a plethora of possible P waves:  use your common sense and don’t call every small quiver in the tracing a P wave; instead look for deflections as big as the balls of Bulldog Drummond.

The Scarlet Pimpernel
The Scarlet Pimpernel  was  written by Emma Orczy  (aka Baroness Orczy) in 1904 and is set at the start of the French Revolution.  The main  character is Sir Percy Blakeney,  a wealthy English baronet who presents himself in everyday life as a dim-witted, foppish playboy.  In the third series of Blackadder Hugh Laurie depicted the Prince Regent as a complete fop and idiot in a manner that resembles Sir Percy.
Sir Percy has an alter-ego where he disguises himself as the masked Scarlet Pimpernel and rescues individuals sentenced to death by the guillotine.  After each rescue he leaves behind a card showing a small flower - a scarlet pimpernel.
The French authorities are driven to distraction by the Scarlet Pimpernel, but are unable to capture him despite their best efforts.  Baroness Orczy wrote these unforgettable lines about the SP:
“They seek him here, they seek him there
Those Frenchies seek him everywhere
Is he in heaven or is he in hell?
That demned elusive Pimpernel”
These words can come to mind when looking for P waves in arrhythmias.
Trying to deduce the mechanism of an arrhythmia at times requires “brains” and the ability to simplify the complex.  To quote the Baroness

“Money and titles may be hereditary," she would say, "but brains are not”.
‘It does seem simple, doesn't it?' she said……’when you want to kill a chicken...you take hold of it...then you wring its neck...it's only the chicken who does not find it quite so simple’.